Fan motor suspension mount for a combustion-powered tool

ABSTRACT

A motor mount for suspending a fan motor in a combustion-powered tool includes an inner ring for securing to the motor, an outer ring that is secured to a portion of the tool, and a web portion disposed between and connecting the inner ring and outer ring. The inner ring, outer ring, and web portion are formed as a unitary piece. Preferably, the mount is formed of a thermoplastic polyester elastomer.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to improvements inportable, combustion-powered fastener driving tools, and moreparticularly to a mount for a combustion chamber fan motor.

[0002] Portable, combustion-powered fastener driving tools are used fordriving fasteners into workpieces. Exemplary embodiments of fastenerdriving tools are described in U.S. Pat. Nos. 4,522,162; 4,483,473;4,483,474; 4,403,722; 5,197,646; 5,263,439; and Re. 32,452, all of whichare incorporated by reference herein. Particular embodiments of fastenerdriving tools are sold, for example, by Illinois Tool Works of VernonHills, Ill., under the IMPULSE® and TRIMMASTER® brands.

[0003] Tools of the type noted above typically incorporate a generallypistol-shaped tool housing enclosing a small internal combustion engine.The engine is powered by a canister of pressurized fuel gas, also calleda fuel cell. A battery-powered electronic power distribution unitproduces the spark for ignition, and a fan located in the combustionchamber provides an efficient combustion within the chamber andfacilitates scavenging, including the exhaust of combustion by-products.The engine includes a reciprocating piston with an elongated, rigiddriver blade disposed within a cylinder body.

[0004] A valve sleeve is axially reciprocable about the cylinder and,through a linkage, moves to close the combustion chamber when a workcontact element at the end of the linkage is pressed against aworkpiece. This pressing action also triggers a fuel metering valve tointroduce a specified volume of fuel into the closed combustion chamber.

[0005] Upon the pulling of a trigger switch, which causes the ignitionof a charge of gas in the combustion chamber of the engine, the pistonand driver blade are shot downward to impact a positioned fastener anddrive it into the workpiece. The piston then returns to its original or“ready” position through differential gas pressures within the cylinder.Fasteners are fed magazine-style into the nosepiece, where they are heldin a properly positioned orientation for receiving the impact of thedriver blade.

[0006] Upon ignition of the combustible fuel/air mixture, the combustionin the chamber causes the acceleration of the piston/driver bladeassembly and the penetration of the fastener into the workpiece if thefastener is present. This combined downward movement causes a reactiveforce or recoil of the tool body. Hence, the fan motor, which issuspended in the tool body, is subjected to acceleration in a directionopposite the power stroke of the piston/driver blade and fastener.

[0007] Then, within milliseconds, the momentum of the piston/driverblade assembly is stopped by the bumper at the opposite end of thecylinder, and the tool body is accelerated toward the workpiece.Therefore, the fan motor and shaft are subjected to an accelerationforce that is opposite the direction of the first acceleration. Thesereciprocal accelerations cause the fan motor to oscillate with respectto the tool. The magnitude of these accelerations, if left unmanaged, isdetrimental to the life and reliability of the combustion chamber fanmotor.

[0008] Recent portable, combustion-powered fastener driving toolsaddress the problems of motor acceleration and oscillation by includinga suspension mechanism that suspends the fan motor within a cavity ofthe cylinder head. The suspension mechanism reduces the effects of thereciprocal axial accelerations and the resulting oscillation of themotor during operation of the tool, and allows the use of a standard,iron-core motor in the tool. Before such suspension mechanisms,specially designed motors were required in the tools to withstand thereciprocal accelerations, resulting in increased production costs.

[0009] Exemplary embodiments of such recent suspension mechanisms aredescribed in commonly assigned EP 1 197 300 and EP 0 925 880, theentireties of which are incorporated herein by reference. The type ofsuspension mechanism described in EP '300 and EP '880 suspends themotor, for example, within a depending cavity in the center of acylinder head. The suspension mechanisms include a flexible rubber web,which may be vulcanized or bonded to a retaining mechanism securing thefan motor, such as a retaining ring or cup. The web is also vulcanizedor bonded to a mechanism such as a steel mounting bracket or steel ring,radially spaced from the retaining ring and secured to the cylinderhead. Only the resilient web secures the retaining mechanism holding themotor to the cylinder head. The rubber web may be provided with a numberof preferably blind end bores.

[0010] These and similar types of suspension mechanisms reduce or dampenoperationally-induced reciprocal accelerations of the motor whilekeeping the oscillations of the motor within an acceptable range, thusextending the life of the motor. Because a standard motor can be used ina portable tool having the suspension mechanisms, production costs ofthe tool can be reduced.

[0011] However, it has been difficult and costly to produce the presentsuspension mechanism, due to, among other things, the costs of stampingthe rubber web and vulcanizing or bonding the rubber web. Due tocontinuing commercial pressure on manufacturers to lower prices, thereis a need to provide a combustion chamber fan motor suspension whichsubstantially provides the benefits of prior art suspensions at areduced manufacturing cost.

SUMMARY OF THE INVENTION

[0012] The present invention provides a mount for a fan motor suspensionmechanism of a combustion-powered tool. The tool is of the type thatgenerates an upward axial acceleration of the motor upon a combustion inthe chamber and a subsequent reciprocal axial acceleration of the motor,where at least one of the accelerations causes the motor to oscillaterelative to the tool. The suspension mechanism includes a mount having ainner ring configured to be secured to the motor, an outer ringconfigured to be secured to a portion of the tool, and a web radiallydisposed between and connecting the inner and outer ring. The innerring, outer ring, and web of the mount are a unitary piece.

[0013] Preferably, the web of the mount includes at least onecorrugation for improving or tailoring resilience of the web. The webmay also be separated into at least two sections by one or more gaps.Also, it is preferred that the mount is formed from a thermoplasticpolyester elastomer, such as HYTREL® elastomer made by E. I. DuPont deNemours and Company, of Wilmington, Del.

[0014] In a preferred embodiment of the invention, the tool includes acylinder head that defines at least a part of the combustion chamber,and the outer ring of the mount is secured to the cylinder head by aretaining ring. The inner ring is secured to the motor by a pair ofretaining rings, and suspended at least partially into a cavity of thecylinder head.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a fragmentary side view of a combustion powered fastenertool in accordance with an embodiment of the present invention, the toolbeing partially cut away and in vertical section for purposes ofclarity;

[0016]FIG. 2 is a vertical cross-section of a cylinder head andsuspension mechanism according to an embodiment of the presentinvention, including a first embodiment of the present motor mount;

[0017]FIG. 3 is a perspective view of a second embodiment of a motormount;

[0018]FIG. 4 is a perspective view of a third embodiment of a motormount;

[0019]FIG. 5 is a cross-sectional view of the third embodiment motormount taken along line 5-5 of FIG. 4 and in the direction generallyindicated;

[0020]FIG. 6 is a perspective view of a fourth embodiment of a motormount; and

[0021]FIG. 7 is a cross-sectional view of the corrugation from the motormount of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring now to FIG. 1, a combustion-powered tool of the typesuitable for use with the present invention is generally designated 10.While one type of combustion-powered tool is depicted here, it iscontemplated that other tool configurations and arrangements ofcomponents may be provided that are suitable for use with the presentsuspension. The tool 10 has a housing 12 including a main power sourcechamber 14 dimensioned to enclose a self-contained internal combustionpower source 16, a fuel cell chamber 18 generally parallel with andadjacent to the main chamber 14, and a handle portion 20 extending fromone side of the fuel cell chamber and opposite the main chamber.

[0023] In addition, a fastener magazine 22 is positioned to extendgenerally parallel to the handle portion 20 from an engagement pointwith a nosepiece 26 depending from a lower end 28 of the main chamber14. A battery (not shown) is provided for supplying electrical power tothe tool 10, and is releasably housed in a compartment (not shown)located on the opposite side of the housing 12 from the fastenermagazine 22. Opposite the lower end 28 of the main chamber is an upperend 30. A cap 32 covers the upper end 30 and is releasably fastened tothe housing 12 to protect the fan motor and spark plug. As used herein,“lower” and “upper” are used to refer to the tool 10 in its operationorientation as depicted in FIG. 1; however, it will be understood thatthis invention may be used in a variety of orientations depending on theapplication.

[0024] A mechanically linked fuel metering valve (not shown) such asthat shown in U.S. Pat. No. 4,483,474 may be used. Alternatively, anelectromagnetic, solenoid type fuel metering valve (not shown) or aninjector valve of the type described in commonly assigned U.S. Pat. No.5,263,439 is provided to introduce fuel into the combustion chamber asis known in the art. A pressurized liquid hydrocarbon fuel, such asMAPP, is contained within a fuel cell located in the fuel cell chamber18 and pressurized by a propellant as is known in the art.

[0025] Referring now to FIGS. 1 and 2, a cylinder head 34, disposed atthe upper end 30 of the main chamber, defines an upper end of acombustion chamber 36, and provides a spark plug port (not shown) for aspark plug (not shown), an electric fan motor 40, and a sealing O-ring(not shown). In the present invention, the fan motor 40 is aconventional iron core motor, also known as permanent magnet, brushed DCmotor of the type produced by Nidec Copal of Tokyo, Japan, Canon ofJapan, as well as may other known motor manufacturers. The motor 40 hasan armature shaft end 42 with an armature (not shown) and an armatureshaft 43, and a brush end 45 opposite the armature shaft end.

[0026] The fan motor 40 is slidingly suspended by a fan motor suspensionmechanism, generally designated 50, within a depending cavity 52 in thecenter of the cylinder head 34 that allows for some longitudinalmovement of the motor. As shown in FIG. 2, the motor 40 is preferablyretained in the cavity 52 so that an air gap 54 is created between thelower or armature shaft end 42 of the motor and a floor 56 of the cavity52. The function of the air gap 54 is to provide clearance for the motorduring oscillations occurring in the course of operation. Preferably,the armature shaft 43 extends through a hole 57 of the floor 56.

[0027] As further shown in FIG. 2, the suspension mechanism 50 includesa motor mount, generally designated 60, having an inner, annular ring62, a central, resilient web portion (web) 64, and an outer, annularring 66. The inner ring 62 is configured to contact and secure the fanmotor 40 at a sidewall 63 of the motor, preferably at a portion of themotor longitudinally closer to the brush end 45 than to the armatureshaft end 42. For securing the inner ring 62 to the motor 40, two innerretaining rings 68, such as snap rings, preferably are disposed at leastpartially around the sidewall 63 of the motor and axially surround theinner ring. The inner retaining rings 68 preferably are received into apair of corresponding grooves 70 formed into the sidewall 63, thegrooves having inner walls 71 configured for axially constraining theretaining rings. Thus, the inner ring 62 is sandwiched or axiallyconstrained by the retaining rings 68, and provides an attachment pointfor the motor 40.

[0028] The outer ring 66 of the mount 60 is secured to a portion of thetool 10, and preferably, the cylinder head 34. In the exemplaryembodiment shown in FIG. 2, the outer ring 66 is retained against anannular shoulder 72 of the cylinder head 34. Another retaining ring 74,such as a snap ring having a larger diameter than the pair of retainingrings 68, secures the outer ring to the cylinder head 34. The retainingring 74 is disposed over the outer ring 66 and, when secured, isreceived into a groove 76 formed into the cylinder head and disposedabove the shoulder 72, so that it is axially constrained by inner walls77 of the groove. Thus, the outer ring 66 is axially secured between theshoulder 72 and the retaining ring 74.

[0029] The web 64 extends radially between the inner ring 62 and theouter ring 66, connecting the inner ring to the outer ring. To allow adegree of axial movement by the motor 40, the web 64 is shaped to haveone or more corrugations, folds, or bellows 80. Though corrugations 80are described herein as a preferred structure of the web, it will beunderstood that folds, bellows or similar shapes may be used.Preferably, the corrugations 80 extend axially to one or more peaks 82that do not go beyond the axial outer surfaces of the inner ring 62 andthe outer ring 66, so that the corrugations 80 (including the peaks 82)are recessed in relation to the outer surfaces of the inner ring 62 andthe outer ring 66. The corrugations 80 provide resilience to the web 64,and thus shock absorption for the motor 40.

[0030]FIG. 3 illustrates a second embodiment of a motor mount 100 havinga web 102 with a different configuration than the motor mount 60 shownin FIGS. 1-2. The outer ring 66 contains a recess 83 to allow space forthe spark plug (not shown) disposed within the cylinder head 34. Asshown in FIG. 3, however, the outer ring 66 preferably is continuous, asis the inner ring 62. This helps maintain a constant axial alignment ofthe motor 40 within the cavity 52, reducing misalignment between thearmature shaft 43 and the hole 57 of the cavity. The web 102 in themotor mount 100 is separated into two discontinuous portions 87 by apair of gaps 88 defined by the web. One of the gaps 88 is disposedradially inwardly of the recess 82 to provide clearance for the recess.In the preferred embodiment, the gaps 88 are disposed diametricallyopposite to one another to balance the reciprocating axial movement ofthe motor 40. A pair of keys 90 formed onto and extending radiallyoutwardly from the outer ring 66 is provided for fitting into acomplementary set of recesses (not shown) within the cylinder head 34near the shoulder 72. It is contemplated that the number andconfiguration of the keys 90 may vary to suit the application. Also, itis contemplated that the keys 90 are recesses and the cylinder head 34has a mating key formation. The keys 90 significantly reduce, if noteliminate, rotation of the mount 60 within the cylinder head 34.

[0031] A feature of the mount 60, 100 is that it is formed in a unitarypiece, as opposed to prior art suspension mechanisms having a separaterubber web vulcanized or adhered to metal rings or brackets.Additionally, the mount 60 is preferably formed from a thermoplasticpolyester elastomer, such as HYTREL® elastomer, manufactured by E. I.DuPont de Nemours and Company of Wilmington, Del. The present inventorhas discovered that the mount 60, 100 formed from HYTREL® elastomerprovides a desired amount of resilience for absorbing or dampeningacceleration of the motor 40, while being significantly less expensiveto produce and customize than prior suspensions. The mount 60, 100 mayalso be configured for use with existing combustion tools, replacingmetal/rubber motor mounts in suspension mechanisms.

[0032] The suspension mechanism 50 should be tuned so that, inoperation, the motor 40 does not oscillate excessively with respect tothe tool 10 and either bottom out or top out. By “tuned” it is meantthat the resilience of the motor mount 60, 100 of the suspensionmechanism 50 is adjusted to prevent a particular motor from excessiveoscillation within predetermined, application-specific limits, dependingon the combustion-induced force generated by the particular power source16. As will be appreciated by those in the art, if the mount 60, 100 ismanufactured of HYTREL® elastomer or other thermoplastic polyesterelastomer, it may be molded or otherwise formed into customized shapes,dimensions, etc. for optimizing a tool or for retrofitting.

[0033] Parameters that may be easily varied for tuning the mount 60, 100according to the present invention include the shape of the web 64, 102,the number and height of corrugations, folders, or bellows 80 of theweb, the thickness of the web or the rings 62, 66, and the number, size,and shape of the gaps 88, between portions of the web (and consequently,the number of the portions 87 of the web). Using HYTREL® elastomer orsimilar material to construct the mount 60, 100 allows easy design andproduction of mounts varying in one or more of these parameters.

[0034] For example, FIGS. 4 and 5 depict a third embodiment motor mount110 having a single gap 112 and a web 114. FIGS. 6 and 7 depict a fourthembodiment motor mount 120 having six gaps 122 and six sections 124,with a web 126. A comparison of FIGS. 5 and 7 also shows an example ofvarying shapes between the web 114 and the web 116. For example, FIG. 5illustrates that the web 114 has wave-like corrugations 80 incross-section having an upper peak 82 and a lower dip 92 (as shown inthe orientation of FIG. 5) separated by a relatively straight drop 94.This configuration allows less restrictive travel by the motor 40. FIG.7, by contrast, shows the web 116 having a generally M-shaped,sinusoidal cross-section, having a pair of the corrugations 80 with twopeaks 82 (as shown in the orientation of FIG. 7). The web 64 shown inFIG. 2, furthermore, includes a single corrugation 80. One skilled inthe art will appreciate that a significant number of embodiments arepossible for the mount 60, 100, 110, 120 by varying the parameterslisted above and other parameters known to those of ordinary skill inthe art, and that all of these are contemplated by the presentinvention.

[0035] Referring again to FIG. 1, the generally cylindrical combustionchamber 36 opens and closes by sliding motion valve member 130, which ismoved within the main chamber 14 by a workpiece contacting element 132on the nosepiece 26 using a linkage in a known manner. The valve member130 serves as a gas control device in the combustion chamber, andsidewalls of the combustion chamber are defined by the valve member 130,the upper end of which sealingly engages the O-ring (not shown) to sealthe upper end of the combustion chamber. A lower portion 136 of thevalve member 130 circumscribes a generally cylindrical body or cylinder138. An upper end of the cylindrical body 138 is provided with anexterior O-ring (not shown) which engages a corresponding portion of thevalve member 130 to seal a lower end of the combustion chamber 36.

[0036] Within the cylinder body 138 is a reciprocally disposed piston144 to which is attached a rigid, elongate driver blade 146 used todrive fasteners (not shown), suitably positioned in the nosepiece 26,into a workpiece (not shown). A lower end of the cylinder body defines aseat 148 for a bumper 150 which defines the lower limit of travel of thepiston 144. At the opposite end of the cylinder body 138, a piston stopretaining ring 152 is affixed to limit the upward travel of the piston144.

[0037] Located in the handle portion 20 of the housing 12 are thecontrols for operating the tool 10. A trigger switch assembly 154includes a trigger switch 156, a trigger 158, and a biased triggerreturn member 160. An ECU 162 under the control of the trigger switch156 activates the spark plug (not shown).

[0038] In operation, as the trigger 158 is pulled, a signal is generatedfrom the ECU 160 to cause a discharge at the spark gap of the spark plug38, which ignites the fuel that has been injected into the combustionchamber 36 and vaporized or fragmented by a fan 164. The fan 164 isdriven by the armature shaft 43, and is located within the combustionchamber 36 to enhance the combustion process and to facilitate coolingand scavenging. The fan motor 40 is preferably controlled by a headswitch and/or the trigger switch 156, as disclosed in more detail in theprior patents incorporated by reference.

[0039] The ignition forces the piston 144 and the driver blade 146 downthe cylinder body 138 until the driver blade contacts a fastener anddrives it into the substrate as is well known in the art. The pistonthen returns to its original, or “ready” position through differentialgas pressures within the cylinder, which are maintained in part by thesealed condition of the combustion chamber 36.

[0040] The fan motor 40 experiences two primary accelerations duringthis cycle. First, when the ignition of combustible gases in the chamber36 forces the piston 144 downwardly toward the workpiece, and preferablyforces a fastener into the workpiece, the tool 10 experiences anopposing upward force, or a recoil force, in the opposite direction. Thefan motor 40, which is suspended by the suspension mechanism 50 in thetool 10, is accelerated upwardly in the direction of the recoil of thetool by a force transmitted through the suspension mechanism.Furthermore, the armature shaft 43 is accelerated in the same directionby having constrained movement relative to the motor 40 within limits ofaxial play. Then, in less than approximately ten milliseconds, thepiston 144 bottoms-out in the cylinder against the bumper 150. Thisaction changes the acceleration of the tool 10 towards the workpiece.Therefore, the motor and shaft are now accelerated in this new, oppositedirection. The suspension mechanism 50 and the motor mount 60, 100, 110,120 of the present invention provide a shock absorbing and isolatingsystem to minimize the operational dynamics of the main chamber 14caused by the combustion on the motor 40 and also to protect the motorfrom axial acceleration and large oscillations.

[0041] The motor mount 60, 100, 110, 120 suspendingly supports the motor40 and decreases acceleration of the motor resulting from the combustionduring operation. The motor mount 60, 100, 110, 120 also (preferablywhen properly tuned) dampens oscillation and dynamically operateswithout detrimental contact within the positive constraints of the tool10 (bottoming or topping out). The motor mount 60, 100, 110, 120anticipates the two opposite accelerations separated by a predeterminedfairly repeatable time and resiliently constrains the motor 40,preferably within the bounds of the cavity 52, to minimize theacceleration force of “g's” witnessed by the motor. The motor 40 neednot be custom designed to provide for the acceleration forces generatedby the tool 10. Instead, with the suspension mechanism 50 able to absorbthe acceleration and dampen the oscillation, a less expensive motor maybe provided, which reduces the overall manufacturing cost of the toolwithout impairing performance.

[0042] One skilled in the art will appreciate that the motor mount 60,100, 110, 120 can be designed and/or tuned using variations as describedabove, and as shown by example in FIGS. 1-7, to optimize the support anddampening characteristics of the mount for the motor 40.

[0043] The present invention thus provides a motor mount for asuspension mechanism of a portable combustion-powered tool thatpreferably is inexpensively made, is easily tuned, and may beretrofitted into some existing tools, including tools having standardmotors. The inventive mount provides benefits of previous steel/rubbersuspension mechanisms at a lower cost.

[0044] While particular embodiments of the present mount forcombustion-powered tool of the invention has been shown and described,it will be appreciated by those skilled in the art that changes andmodifications may be made thereto without departing from the inventionin its broader aspects and as set forth in the following claims.

What is claimed is:
 1. A suspension mechanism for a fan motor of acombustion chamber in a combustion-powered tool for driving a fastenerinto a workpiece, the tool generating an upward axial acceleration ofthe motor upon a combustion in the chamber and a subsequent reciprocalaxial acceleration of the motor, at least one of the accelerationscausing the motor to oscillate relative to the tool, the suspensionmechanism comprising: a mount having an inner ring configured to besecured to the motor, an outer ring configured to be secured to aportion of the tool, and a web radially disposed between and connectingsaid inner and outer ring, said inner ring, outer ring, and web being aunitary piece.
 2. The suspension mechanism of claim 1 wherein said outerring is configured to be secured to a cylinder head of the tool.
 3. Thesuspension mechanism of claim 2 wherein said inner ring is configured tobe secured to said motor and suspend said motor at least partiallywithin a cavity of said cylinder head.
 4. The suspension mechanism ofclaim 1 wherein said mount is formed of a thermoplastic polyesterelastomer.
 5. The suspension mechanism of claim 4 wherein said mount isformed of HYTREL® elastomer.
 6. The suspension mechanism of claim 1wherein said web defines at least one gap so that said web is separatedinto at least two portions.
 7. The suspension mechanism of claim 1wherein said web includes at least one corrugation.
 8. The suspensionmechanism of claim 7 wherein said at least one corrugation defines apeak.
 9. The suspension mechanism of claim 8 wherein said web defines atleast one gap so that said web is separated into at least two portions.10. The suspension mechanism of claim 1 wherein said web has a generallywave-like cross-section.
 11. The suspension mechanism of claim 1 whereinsaid web has corrugations that extend to at least an upper peak and alower dip.
 12. The suspension mechanism of claim 1 wherein said web hasat least two corrugations.
 13. The suspension mechanism of claim 1wherein said web has an M-shape in cross-section.
 14. Acombustion-powered tool for driving a fastener into a workpiece, thetool comprising: a combustion chamber defined at least in part by acylinder head; a combustion chamber fan having a motor; and a suspensionmechanism for suspending said motor within the tool, said suspensionmechanism including an inner ring secured to said motor, an outer ringsecured to said tool, and a web portion disposed between and connectingsaid inner ring and outer ring; wherein said inner ring, outer ring, andweb portion are a unitary piece.
 15. The tool of claim 14, wherein saidinner ring, outer ring, and web portion are formed from a thermoplasticpolyester elastomer.
 16. The tool of claim 14, wherein said inner ringis secured to said motor by at least one retaining ring.
 17. The tool ofclaim 14, wherein said retaining ring comprises a snap ring.
 18. Thetool of claim 14, wherein said outer ring is secured to said cylinderhead by a retaining ring.
 19. The tool of claim 18, wherein saidretaining ring comprises a snap ring.